Sunday, March 02, 2008

Foveon X3(R) direct image sensor

An entirely new way to capture color.

Introducing the Foveon X3® direct image sensor, a new
generation of technology that works just like film.

The Foveon X3 direct image sensor is the most advanced color image sensor ever developed. It represents a giant leap forward in color photography and is the only image sensor technology that combines the power of digital with the essence of film.

A direct image sensor is an image sensor that directly captures red, green, and blue light at each point in an image during a single exposure. Foveon pioneered the development of the direct image sensor using the most advanced developments in semiconductor design, image processing, and signal processing. Here is how it compares to film and typical CCD image sensors.

For over 100 years, color film has traditionally been held as the gold standard for photography. It produces rich, warm tones and incredible color detail that consumers around the world have become accustomed to. Film has achieved this by using three layers of emulsion to capture full color at every point in the image.

Charged Couple Device (CCD) image sensors were developed approximately 30 years ago, ushering in the era of digital photography. Unfortunately, the rich, warm tones and detail of color film that the world came to expect from film based cameras were not achievable with the new digital cameras. This was due to the fact that CCD digital image sensors were only capable of recording just one color at each point in the captured image instead of the full range of colors at each location.

Foveon X3® direct image sensor
Finally, Foveon has combined the best of what both film and digital have to offer. This is accomplished by the innovative design of the three layer Foveon X3 direct image sensor. Similar to the layers of chemical emulsion used in color film, Foveon X3 image sensors have three layers of pixels. The layers of pixels are embedded in silicon to take advantage of the fact that red, green, and blue light penetrate silicon to different depths – forming the first and only image sensor that captures full color at every point in the captured image.


A Dramatically Different Design
The revolutionary design of Foveon X3 direct image sensors features three layers of pixels. The layers are embedded in silicon to take advantage of the fact that red, green, and blue light penetrate silicon to different depths — forming the world's first direct image sensor.

From point-and-shoot digital cameras to high-end professional equipment, Foveon X3 technology offers multiple benefits to consumers and manufacturers alike. At the same time, it opens the door for other innovations, such as new kinds of cameras that record both video and still images without compromising the image quality of either.
Pixel Counting Definitions

Prior to the existence of the Foveon X3 direct image sensor, there has been a 1:1 relationship between the number of pixels (photodetectors) and the number of pixel locations for a traditional CCD and CMOS image sensor. Given this relationship, the generic term "pixel" has been commonly used to reference both the pixel (photodetector) and the pixel location. Foveon direct image sensors are a new type of image sensor that incorporates three pixels(photodetectors) at every pixel location on the image sensor. The  definition of a pixel as indicated below is consistent with standard industry conventions as applied to CCD image sensors, CMOS image sensors, and the Foveon X3 direct image sensor.

A pixel on the image sensor of a digital camera is a light absorbing element (photodetector) that converts light (photons) into electrons. A pixel is also referred to as a pixel sensor when there is a need to distinguish the pixel from its location.

Pixel Location
A pixel location is the X,Y coordinate on the two-dimensional grid of an image sensor at which the pixel is located.

A Foveon X3 direct image sensor consists of three layers of pixels. Each pixel detects 1 color sample.

To capture the color that other image sensors miss, Foveon X3® direct image sensors use three layers of pixels embedded in silicon. The layers are positioned to take advantage of the fact that silicon absorbs different wavelengths of light to different depths. The bottom layer records red, the middle layer records green, and the top layer records blue. Each stack of pixels directly records all of the light at each point in the image.

Click here for an Interactive Tutorial

Until now, all other image sensors have featured just one layer of pixels, capturing just one color per point the image. To capture color, the pixel sensors in CCD and CMOS image sensors are organized in a grid, or mosaic, resembling a three-color checkerboard. Each pixel is covered with a filter and records just one color—red, green, or blue.

That approach has inherent drawbacks, no matter how many pixels a mosaic-based image sensor might contain. Since mosaic-based image sensors capture only one-third of the color, complex processing is required to interpolate the color they miss. Interpolation leads to color artifacts and a loss of image detail. Blur filters must then be used to reduce color artifacts. The use of blur filters adversely affects  sharpness and resolution of the final image captured.

With its revolutionary process for capturing light, Foveon X3 technology never needs to compromise on quality, so you get sharper pictures, truer colors, and fewer artifacts. And cameras equipped with Foveon X3 technology do not have to rely on processing power to fill in missing colors, reducing hardware requirements, simplifying designs and minimizing lag time between one shot and the next.

A Side-by-Side Comparison

Foveon X3® technology visibly improves image quality, as these comparisons demonstrate. In this case, an image taken with a mosaic sensor is compared to an image taken with Foveon X3 technology. Both image sensors are the same physical size, however the X3 direct image sensor has three times the number of pixels.

Mosaic Picture
Foveon X3 Capture

For an interactive demonstration click here


Mosaic Capture
Foveon X3

Color Detail
Mosaic Capture
Foveon X3

Mosaic Capture
Foveon X3